My HD650 cable died (again). Waiting for non OEM cable to arrive. I had Audio Technica ATH-M40x drivers with an open wood cup laying around. Friction fit it right in to the HD650 headband. The headband has a handkerchief instead of the pads (they go flat through the years). The M40x pads fake leather was coming off heavily. So I took it all off and now the pads are just fabric. Cut some round foam to cover the back of the drivers. That cable on top I soldered on to connect the left and right driver (M40x only has one input on the left). It works fine as long as I am careful with it (so the drivers don't fall off the headband). Surprisingly, making the M40x open back doesn't change the sound much at all. It is a downgrade from my HD650 though. It's a bit cursed but I'm still enjoying the music.